Those Conservatives talking up the prospects of EU withdrawal are putting party before country. Shame on them.

The Conservative Party hasn’t won a general election for over two decades and its latest infighting on Europe suggests that this trick may get repeated. Internal divisions on Europe haven’t been the sole cause of the Tories' poor record. A big reason has been the growth of multiparty politics: Liberal Democrats in government in Westminster; the Scottish National Party in power in Holyrood. And with Ukip moving from a single issue party to a party of right-wing protest, Britain’s multi-party politics looks even more daunting for the Conservatives. How they respond to the strongest UKIP threat ever may well determine the next election. Do they appease Ukip or confront them?

So far, Conservative appeasers are winning. Talk of pacts with Ukip and even more hostility to Europe and migrants is leaving the Prime Minister’s modernisation strategy rather ragged. Yet that strategy was informed by analysis showing that for every vote they gained on the right, they lost one on the centre. The votes they will gain by aping Ukip will almost certainly be in the wrong places, pushing an overall majority further way. For Liberal Democrats, a Conservative rightward shift replacing their past strategy of "love–bombing" seems like a return to business as usual. It also underlines how we, in this coalition, are preventing the right taking control of the government tiller.

What the Conservatives haven’t understood is that Ukip's new trick has not been to talk more about Europe, but to talk less about Europe. Its recent focus is on immigration and crime. With the economy and jobs top in voters’ minds – and Europe low - the Tories are repeating their 2001 and 2005 mistakes.

The one positive outcome of Ukip's new profile may be a greater focus on the party. Nigel Farage has an easy charm but, like all snake-oil salesmen, he obscures his product’s reality. Ukip's manifesto is not a serious policy platform for government. Its performance in the European Parliament is shameful. Since 2009, Farage has attended just one in over 30 meetings of the fisheries committee, where he is supposed to fight for British interests.

Perhaps a Lib Dem should stop giving political advice to the Conservatives – we have problems of our own. However, I hope it doesn’t sound too sanctimonious when I say that the reason I have overcome my tribal loyalties is the national interest.

People need to wake up. When cabinet ministers follow Tory grandees in backing withdrawal from the EU and when the Conservative Party votes against its own Queen’s Speech, stakes have risen. The best we now have from the Conservatives when it comes to pursuing our national interest in Europe is to threaten our partners with renegotiation and an "in our out" referendum, whatever is negotiated. It’s like a hostage taker-saying, "If you give me what I want, I still might shoot you."

Is there another way? My experience in government suggests there is. Britain’s interests can be served by reforming the EU from within. As a business minister, I became frustrated with the slow pace of economic reform in the EU – despite conclusions from European Councils saying the right things. So I set up a new ginger group, working with fellow EU Ministers who share the British view that the EU needs to boost competitiveness.

This informal like-minded group – the EU Group for Growth – quickly attracted 16 member states. We went on, among other things, to secure the most significant shift in EU regulatory approach for decades: default small-business exemptions from all new EU regulations; a review of the most burdensome regulations for business; and the ability to drop pipeline proposals that could pose excessive costs. You won’t have read about it, but it’s the beginnings of real EU reform.

Now, as Energy and Climate Change Secretary, I have set up a Green Growth Group of 10 fellow Environment Ministers. To ensure we can green the EU economy and remain competitive - and ensure the EU continues as a leading bloc in climate change talks – such co-operation is essential. We won’t reform the EU’s flagging carbon market or encourage low carbon energy without such engagement and leadership.

The Prime Minister’s success on curbing the EU budget didn’t come from megaphone diplomacy. It came from the hard graft of coalition-building and persuasion. And when the Prime Minister is rightly trying to build momentum for an EU-US trade deal worth tens of billions of pounds, rampant speculation about a "Brexit" only damages the prospects of its success.

Ukip’s policies on crime and immigration should also be confronted. Its opposition to Europol and the European arrest warrant is a charter for terrorists and organised criminals to return to the time when crossing a country’s borders meant escaping justice.

The real fight is about immigration. It is not a new issue. Britain wasn’t an EU member when Enoch Powell gave his rivers of blood speech. The bureaucratic mess in Britain’s immigration system has nothing to do with the EU. Everything to do with poor management and policy - problems the Coalition is beginning to fix.

While the Conservative-backed EU enlargement did lead to a rise in eastern-European migration, less than one in three immigrants to Britain comes from the EU. Moreover, EU migrants more than pay their way. Between 2004 and 2009, EU migrants paid 37 per cent more in tax than they received in public services and were 59 per cent less likely to be on welfare benefits than British nationals.

What is Ukip offering the more than one million Brits living elsewhere in the EU? Some 260,000 of us work in another EU country every year. And at least 450,000 have retired in another EU country. There may well be more UK citizens living in EU countries than EU citizens living in the UK: Ukip proposes swapping hard-working young Poles with retired, elderly Brits from Spain.

As for a referendum, the coalition’s constitutional reforms make a vote on Europe inevitable if any new treaty is proposed. I, for one, would relish the opportunity to make the case that Britain’s national interest demands we stay in the EU. But trying to hold a gun to the head of our EU partners is not a way to negotiate. Why should others in Europe accommodate British interests if we are heading to the door?

By talking up the prospects of withdrawal, those Tories are damaging our national interest not strengthening it. And they are doing so on the false promise that it will help them win a general election. This is a clear case of putting party before country. Shame on them.